Improve algorithm for determining start measure for note input
When you enter note input mode, we try to find a good place to start based on the current selection.
If nothing is selected, we take the first currently-displayed measure. I propose checking first to see what the last-selected CR is and using that instead, if it is in view (last selected CR is something only now available to us in 3.3).
If a note or rest is selected, we start there, no changes proposed.
If something other than a note or rest is selected, we look up the parent chain until we find a measure and start there. But, this fails if something is selected that is not a descendent of measure - that includes spanners, beams, and frames. I propose we simplfy this code to just use tick of the element (something that wasn't always available when this code was originally written).